Beams of high intensity UV light are useful for curing polymers in coatings, inks, adhesives and the like, and for other purposes. A known reliable source of UV light at good power is the mercury vapor street light. Typical power is 175 watts per inch available a few minutes after starting. At start-up a small pool of mercury is vaporized and heated. The lamp is a negative resistance device requiring ballast to prevent increasing current from damaging the lamp. The negative resistance is offset by a positive impedance that tends to limit current. As the lamp heats up during operation, internal gas pressure rises and a higher voltage is required to maintain the discharge. The resistive drop across the ballast supplies the required voltage until the required voltage cannot be supplied to maintain the discharge. At that point, the discharge is extinguished, the lamp cools, the gas pressure is reduced and the ballast is again effective once the lamp is started. An auxiliary high voltage electrode is used to restart the arc discharge. In the prior art, filaments of incandescent lamps have been placed in series with filaments of UV germicidal lamps as electrical ballast in household clothes dryers.
For UV beams with high power, say over 100 watts per inch with a beamwidth of 1 to 5 inches at a distance from the beam of one or two inches, large housings are used to provide room for both circuitry, lamp and any cooling structures. What is needed is a hand held structure that will hold apparatus for a moderate power UV beam device. A hand held device offers speed and precision for curing of polymer coating on surfaces of all shapes.